# Understanding Electrode Potentials: Why is 1/Molarity Used in the Calculation?

• Puchinita5
In summary, the conversation revolves around calculating electrode potential for a silver filled electrode in a solution of 0.00550 M AgNO3. The correct equation for Nernst equation is discussed, with an explanation for the use of 1/.00550M in the parenthesis. The concentration of NO3- does not affect the calculation.
Puchinita5
I don't know why, but I just can't figure this out.

"Calculate the electrode potential for a silver filled electrode in a solution of 0.00550 M AgNO3 solution."

I got that

Ag+ + e- --> Ag(s) had an E* = .80V

I got that the answer is E=.80 - .0592 log (1/.00550M)= .6655 V

But why do you put 1/.00550M in the parenthesis?

My first thought was that AgNO3 + e- --> Ag(s) + NO3-
and that the concentreation of AgNO3 is the same as NO3.

so that it would be log(1) , which is wrong.

I just don't get the concept I guess.

It all depends on how you write the Nernst equation. There are two conventions:

$$E = E_0 + \frac {RT}{nF} ln \frac{[Ox]}{[Red]}$$

and

$$E = E_0 - \frac {RT}{nF} ln \frac{[Red]}{[Ox]}$$

(personally I prefer the first one, but that's just because I was taught this way).

Note that both equations are equivalent thanks to the sign change.

Oxidized form of silver is Ag+, reduced form is a metallic Ag - with activity equal to 1. So you can write the equation either as

$$E = 0.88 + 0.059\ log([Ag^+])$$

or

$$E = 0.88 - 0.059\ log\big(\frac 1 {[Ag^+]}\big)$$

Concentration of Ag+ is 0.00550 M, concentration of NO3- doesn't matter.

oh! okay that makes sense. I don't know why but I always confuse myself with these electrode problems.

Thank you!

## What is an electrode potential?

An electrode potential is a measure of the tendency of an electrode to lose or gain electrons in a chemical reaction. It is a measure of the ability of an electrode to conduct electricity.

## What factors affect electrode potential?

The factors that affect electrode potential include the nature of the electrode material, the concentration of ions in the solution, and the temperature of the solution.

## How is electrode potential measured?

Electrode potential is typically measured using a standard hydrogen electrode as a reference. The electrode potential is measured by connecting the electrode to a voltmeter and measuring the voltage difference between the electrode and the reference electrode.

## What is the significance of electrode potential in electrochemistry?

Electrode potential is a key factor in determining the direction and extent of chemical reactions in electrochemical cells. It is also important in determining the efficiency and selectivity of electrochemical processes.

## How can electrode potential be manipulated in electrochemical systems?

Electrode potential can be manipulated by changing the conditions of the electrochemical system, such as the concentration of ions, temperature, and the type of electrode material used. It can also be controlled by applying an external voltage to the system.

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